Well water is normally drawn out of the well by using a system including either a jet pump motor with impeller above ground or by using a system including a submersible pump motor and staged submersible pump end.
In the jet pump system, the jet pump motor with impeller is above the ground and is creating suction to draw water upwardly from the well through the jet pump impeller. Most of the water leaving the jet pump is recirculated back into the well through a well water ejector to help in drawing the water from the well. The rest of the water leaving the jet pump impeller is delivered to the water service system.
The maximum theoretical efficiency for a jet pump system is approximately 30%. However, the majority of the jet pump well systems operate in an efficiency range between 15% and 20%. The jet pump system is less expensive and easier to maintain than the submersible pump.
In a submersible pump system, the pump motor, screened inlet and submersible pump end are positioned in the well casing below the water level. The submersible pump end has plural stages to develop high water pressures of 100 to 120 psi to create a strong pressure effect and to forcibly direct the water upwardly out of the well. Submersible pumps operate at higher efficiencies, for example in the efficiency range of 40 to 60%, but are subject to other disadvantages.
For example, submersible pumps are more expensive than jet pumps. Also, submersible pumps are subject to additional operational problems, increased maintenance and increased expenses due to their submerged position in the well casing and due to particulate materials in the well water.
These jet pumps and submersible pumps have been used in systems to remove contaminants by filtering the raw well water. Two systems removing well water contaminants by filtration are disclosed in McLean U.S. Pat. No. 3,649,532 and in Patterson U.S. Pat. No. 4,430,228.
In the McLean patent, the pumped well water passes through a venturi type apparatus to entrain air into the water, and this air laden water is then introduced into a filter tank containing a filter bed. The air intake at McLean's venturi is limited so as not to oxidize the iron contained in the water before it enters the filtration bed. This filtration bed slowly raises the pH of the water passing therethrough while oxidizing and filtering the iron hydroxide and other impurities therefrom. The single filtration tank McLean system has an air inlet that must be closely controlled to avoid oxidation of the contaminants until the water enters the filter bed.
The Patterson patent also includes using an air injector to introduce air in controlled quantities to form colloidal iron compounds in the water in the form of invisible sols having charged micelles. The water with colloidalized iron having charged micelles is passed through filter tank particulate material having opposite surface charges capable of attracting, removing and collecting the dispersed iron hydrate cells. The Patterson patent thus teaches closely controlling the injection of air to create colloidalized, electrostatically charged, hydrated micelles which are removed in a single filter tank having a specialized media bed preconditioned at the factory to have an opposite electrostatic charge.
To improve upon the single tank filtering systems with closely controlled, limited air inputs, two of the inventors of the present application developed a system entraining substantially more air than required for oxidation purposes and employing an aeration and precipitation tank in addition to a filter tank. This improved system is disclosed and claimed in Chandler application Ser. No. 659,327 which was filed on Oct. 10, 1984 now U.S. Pat. No. 4,659,463 and is assigned to the assignee of the present invention. The systems utilizing the invention disclosed in the Chandler application have improved the quality of water delivered to service when satisfactory operating conditions exist.
In this regard, in order to entrain excess air substantially to oxidize the contaminants, a pressure differential of at least 15 psi across the venturi nozzle is required. When the Chandler system is retrofit into a jet pump system, the required pressure differential across the air intake manifold assembly may not always be enough to entrain sufficient excess quantities of air. In such a situation, the jet pump could be replaced by a relatively expensive submersible pump having the operational and maintenance problems involved with submersion in well water. With either type of pump, all the excess air had to be entrained in one pass through the air mixing manifold and aeration and precipitation tank. While one pass normally provides satisfactory results, certain water conditions may exist where water quality could be enhanced by additional air exposure with resultant additional oxidation of contaminants contained therein.
Moreover, certain abnormal operating conditions can exist which are detrimental to the McLean, Paterson or Chandler well water systems employing either type of pump. For example, if a faucet is inadvertently left on in the house, the water continuously delivered to the house may exceed the capacity of the system to withdraw water from the well, particularly in a weak well situation. When this happens in a jet pump system, the pump loses its prime, which at best requires the system to be reprimed and restarted and which at worst results in pump motor or impeller damage. When this happens with a submersible pump system, the submersible pump, if equipped with valve or switch safeguards, will shut off requiring restarting. If the submersible pump is not equipped with safeguards or they fail, the submersible pump ultimately would no longer be submerged and could experience air locking or pump damage.